1. Field of the Invention
An Aspect of the present invention relates to a disk, and more particularly, to a recording/reproducing apparatus for efficiently managing a read-modify-write (RMW) process for a logical overwrite (LOW), a recording/reproducing method therefore, and an information storage medium therefor.
2. Description of the Related Art
A spare area is generally prepared in a portion of a data area in a rewritable information storage medium. If a defect is detected while user data is being recorded in a user data area (an area obtained by excluding the spare area from the data area) or while data recorded in the user data area is being reproduced, replacement data for replacing the defect data is recorded in the spare area.
For write-once information storage media, the above defect management method is used in a logical overwrite (LOW). LOW is a method by which write-once information storage media are useable similarly with the rewritable information storage media. That is, to update data previously recorded in the user data area, data for replacing the recorded data is recorded in the spare area by treating the recorded data as defect data. This makes data management easy since a host accesses data using a logical address thereof and the data for replacing the recorded data in the user data area appears to be overwritten at the same location by using the fixed logical address of the data recorded in the user data area and assigning a physical address corresponding to the fixed logical address to the data recorded in the spare area.
To maximize utilization of the disk capacity, a method of updating data by LOW during defect management in a unrecorded area of a user data area on a disk or a spare area and generating replacement information for the updated data (replacement entry information) has been suggested to maximize the use of the disk.
Data updating by replacement by LOW and replacement by defect will now be schematically described with reference to FIGS. 1A and 1B.
FIG. 1A illustrates LOW replacement according to the prior art. Referring to FIG. 1A, when data blocks A1, A2, and A3 have been recorded at physical locations P1, P2, and P3 on a recording medium, respectively, if a host commands a drive system to record data blocks B1, B2, and B3 at the original locations P1, P2, and P3 to update the data blocks A1, A2, and A3 to the data blocks B1, B2, and B3 by LOW, the drive system records the data blocks B1, B2, and B3 at physical locations P4, P5, and P6 in a user data area on the medium and generates a defect list (DFL) entry indicating that the original locations P1, P2, and P3 were replaced with the replacement locations P4, P5, and P6.
Thereafter, if the host commands the drive system to reproduce the data blocks B1, B2, and B3 from logical addresses corresponding to the original locations, the drive system reproduces the data blocks B1, B2, and B3 recorded at the replacement locations P4, P5, and P6 by referring to the DFL entry and transmits the reproduced data blocks B1, B2, and B3 to the host. When the drive system cannot reproduce the data blocks B1, B2, and B3 recorded at the replacement locations P4, P5, and P6, it cannot be guaranteed for the data recorded at the replacement locations to be the same as the data recorded at the original locations since the replacement locations P4, P5, and P6 are located in the user data area. So, the drive system continuously retries to reproduce the data blocks B1, B2, and B3 recorded at the replacement locations P4, P5, and P6, and if the drive system fails to reproduce the data blocks B1, B2, and B3, the drive system informs the host that the data blocks B1, B2, and B3 cannot be reproduced.
FIG. 1B illustrates defect replacement according to the prior art. Referring to FIG. 1B, when a host commands a drive system to record data blocks A1, A2, and A3 at logical addresses corresponding to original locations P1, P2, and P3 on a medium, respectively, the drive system detects a defect at the physical location P2 while recording the data blocks A1, A2, and A3 at the physical locations P1, P2, and P3, records the data block A2 at a replacement location P5 in a spare area by replacing the original location P2 with the replacement location P5, and generates a DFL entry indicating that the original location P2 was replaced with the replacement location P5.
Thereafter, if the host commands the drive system to reproduce the data block A2 at the logical address corresponding to the original location P2, the drive system reproduces the data block A2 recorded at the replacement location P5 by referring to the DFL entry and transmits the reproduced data block A2 to the host. If the drive system cannot reproduce the data block A2 recorded at the replacement location P5 due to a defect, the drive system regards the data block A2 recorded at the original location P2 as being the same as the data block A2 recorded at the replacement location P5 since P5 is the replacement location in the spare area. Accordingly, even if the drive system cannot reproduce the data block A2 recorded at the replacement location P5, the drive system tries to reproduce the data block A2 recorded at the original location P2. If the data block A2 recorded at the original location P2 is error-correctable, the drive system can transmit the error-corrected data block A2 to the host.
To maximize utilization of disk capacity and manage disks by discriminating between LOW replacement and defect replacement, methods of using disks by discriminating between an area for replacement by LOW and an area for replacement by defect have been developed. In one of them, an area for replacement by defect is limited to a spare area allocated for conventional replacement by defect and an area for replacement by LOW is limited to a user data area of a data area or a specific area of the user data area except the spare area. Thus, whether data at a replacement location has been recorded by replacement by LOW or replacement by defect can be determined by confirming an area in which the replacement location of a DFL entry (also called a replacement entry, a defect entry, or a defect/replacement entry) exists.
For write-once information storage media, user data of a replacement block after replacement by defect is the same as user data of an original block before the replacement by defect. However, since the replacement by LOW is mainly used to update data, it cannot be guaranteed that user data of a replacement block be the same as user data of an original block before the replacement by LOW. If a replacement block indicated by a DFL entry is located in a spare area, it can be perceived that the DFL entry has been generated due to a defect. Accordingly, user data of an original block can be regarded as being the same as user data of the replacement block. Thus, if the replacement block cannot be error-corrected due to a defect when it is reproduced, the user data can be obtained by reproducing the original block indicated by the DFL entry. In more detail, even if the original block cannot be error-corrected since the original block has been replaced due to the defect, the original block may be sometimes error-corrected by cleaning the dust from a recording surface of a medium.
In this case, the replacement by defect and the replacement by LOW are discriminated from each other to determine whether user data of a replacement block is the same as user data of an original block by recognizing areas in which replacement blocks of the DFL entry for the two replacements are recorded.
In the case of conventional write-once information storage media and apparatuses not using LOW, when data is recorded, a recording timing is limited to a start location of each recording/reproducing unit. Because write-once information storage media cannot be overwritten, a host manages data sector by sector (2048 bytes), and an information recording apparatus records data block by block, each block consisting of a plurality of sectors.
However, when LOW is applied to write-once information storage media, the recording timing does not have to be limited to a recording/reproducing unit, and it is possible to record data in sector units managed by the host. Due to this, a read-modify-write (RMW) process is necessary for the write-once information storage media and apparatuses to update a portion of one block data. However, when data is logically overwritten in partial sectors of a previously recorded block, a drive system reads the block including the partial sectors, modifies the partial sectors of the block, and writes the modified block in a unrecorded area of the medium by replacing the read block with the modified block. On the other hand, when a previously recorded block is reproduced, if the block cannot be reproduced, i.e., if an ECC error is generated, since the block is conceptually a defect block, replacement by defect should be performed. In this state, since an area for replacement by defect and an area for replacement by LOW are discriminated from each other, a replacement block for replacing a block to which replacement by LOW and replacement by defect are simultaneously applied is recorded becomes a problem.